Field of the Invention
The present invention relates to a holding structure for optical sheets used in a display apparatus.
Description of the Related Art
In recent years, liquid crystal display (LCD) modules using an LCD panel and light emitting diodes (LEDs) serving as the light sources of a backlight have become mainstream as display modules used in image display apparatuses. A backlight has a direct structure in which light sources are arranged on the back surface of an LCD panel or an edge light structure in which a light guiding plate and light sources on the lateral side of the light guiding plate are arranged on the back surface of an LCD panel. In any of the backlight structures, a plurality of optical sheets for diffusion and condensing is stacked one on top of another between an LCD panel and LEDs and a light guiding plate to improve image quality characteristics such as brightness and uniformity.
Hereinafter, a description will be given of the structure of a display module and the holding structure of optical sheets in the related art.
An LCD panel is held with its periphery on the outside of a display region sandwiched between a panel case and a panel holder. An LED substrate is accommodated in a box-shaped backlight case having an opening on its panel side. The optical sheets are held with their peripheries on the outside of an illumination region for the LCD panel sandwiched between the panel holder and the backlight case on their front and back surface sides. In addition, the optical sheets are held with their outside shapes creating gaps between the outside shapes and the inside walls of the panel holder so as to be prevented from being in contact with the housing and wrinkling at thermal expansion.
In this structure, there is a likelihood that the sheets rub against each other due to vibration at transportation and get damaged to cause abnormal display. In view of this problem, the related art has proposed a structure shown in FIG. 10. In this structure, optical sheets 110 have positioning shapes including locking holes 110a and slits 110b continuing to the locking holes 110a, and the positioning shapes engage with pins 120 provided on a backlight case (see Japanese Patent Application Laid-open No. 2005-242270).